Radio signals passing through the ionosphere can be affected by small irregularities of the ionospheric plasma. This phenomenon is called radio scintillation and can strongly disturb or disrupt the signal transmission. As a result it can prevent a GPS receiver from locking on to the signal and can make it impossible to calculate a position. Less severe scintillation conditions can reduce the accuracy and the confidence of positioning results.
Transionospheric radio scintillation is statistically characterized by two parameters, amplitude and phase fluctuations indices, denoted respectively by S4 and σφ .
S4 is defined as the ratio of the standard deviation of signal intensity and the average signal intensity. Amplitude scintillations are prominent near the geomagnetic equator. They almost appear regularly in the evening hours.
σφ is defined as the standard deviation of a linearly detrended phase data segment. Phase scintillations are prominent in high latitudes, and their occurrence rate increases with geomagnetic activity.
SARTS received a request for statistics or help in acquiring statistics of ionospheric scintillation in the VHF range. VHF is not a common frequency range used in space infrastructure and there seems to be a lack of statistics in the area between tropics, where the ionosphere is bubbling quite frequently.
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by Philip Lai, 9V1PL
This article was motivated by my fellow HAMs from the satellite group. Based on my success with the application of the concept of EME on 2 m to our SARTS Repeater without line of sight, I hope this write up can help those in the hobby with similar challenges to explore the concept of EME.
Earth-Moon-Earth communication (EME), also known as moon bounce, is a radio communications technique, which relies on the propagation of radio waves from an earth-based transmitter directed via reflection from the surface of the moon back to an earth-based receiver.
The challenge of my location (QTH)
I am located at the South Eastern Coast of Singapore, an apartment dweller with low elevation of 25 m facing south west. The distance to the Singapore VHF repeater is approximately 12 km. The small balcony with an opening of just slightly over 100 degrees is surrounded by tall buildings and makes it difficult for me to reach the repeater located at Dover.
For many months, when I first started as a new HAM, all I could hear was noise from my handheld (HT).
Each time I pushed the PTT, I couldn’t trigger the repeater, but even when I could trigger the repeater, I couldn’t hold it transmitting. It was frustrating, I fully understand, if you are facing similar challenges.
Continue reading Applying the Concept of Earth-Moon-Earth (EME)
In order to improve the coverage of our SARTS VHF repeater and sort out technical problems, it is very helpful to have a list of practical issues experienced during operation. Therefore, please help and report any problem using either this Github link, or our contact form.
Please state your call sign, the power and antenna used with the description of the issue and date/time, when it appeared.